Ensure you are using the Nintendo 3DS AC adapter (Model No. WAP-002 (AUS)). The Nintendo DSi AC adapter is also compatible.
Unplug the AC adapter and wait approximately 30 seconds before plugging it in again. Ensure the AC adapter is securely connected to both the Nintendo 3DS and the electrical outlet.
The battery pack may not be connected correctly if the recharge LED lights up then immediately turns dark. Make sure the battery pack is connected properly.
If the recharge LED is blinking, there is a chance the battery pack may not be connected correctly. If you experience this, contact Nintendo Customer Service.